sujeethmonu,
Following on from the good advice by Gonzo, The work and research to design a boat/ship starts with human needs and your post only scratches the surface, then there is the "engineering stuff" to make the human space work and achieve the purpose of the construction, then there is the ergonomics of human interaction with the machines, space to sleep, toilet (defecate and wash), drink, sleep, and cook and eat and rest. - - Freezer space for food and catch, - - many tonnes for fuel. - - :?: Reverse osmosis watermaker (saves space and weight?), - - flash freezers for the fish, and the list goes on and on.........
Why do you need 7 days duration in India? Fish farming may be the better economic proposition.
At least 3 times your water allocation just for drinking and MORE for tropical work areas, what about washing clothes, washing off the salt, having a shower before evening meal and bed/sleep, water for cooking and general cleaning......